Thermodyamics Definition and 269 Threads

I understand the 1st law of thermodynamics developed as a generalization based on experimental observations, in that an exception has yet to be found in thousands of situations, so it is considered to hold true in all possible situations. If that is how it developed, is there any other theory or...

So recently I've become familiar with concepts like specific heat, and we use a formula Q=mcΔT to calculate the Joules necessary to heat up say a kg of water from 50 to 70 degrees celsius. Now I was wondering if there is a equation that incorporates the amount of heat lost to the atmosphere...

So I worked through the Boltzmann distribution and got: $$ P\propto e^{\frac{-E}{k_BT}} $$ Where $E$ is the energy. So surely this means the kinetic energy (and therefore speed) of particles is distributed over a Boltzmann distribution. Or in equation: $$ P\propto e^{\frac{-mv^2}{2k_BT}} $$...

Does the phonon thermal conductivity account for a large part of the total thermal conductivity in thermoelectric materials like Bismuth Telluride? As far as I know, the phonon conductivity is the largest contributor to the total thermal conductivity in semiconductors. Is this still true for...

Homework Statement What is the net heat flow of an aluminum disk (emissivity = 0.05) with radius 10 cm and temperature 293K placed inside a room where the temperature is 300K? Asurface = π*r2 = 0.01π m2 Homework Equations Hnet = A*e*σ(Tradiate4-Tabsorb4) The Attempt at a Solution By simply...

Hi, From the first law of thermodynamics it follows: Cp * (δT/δt) = (δQ/δt) where Cp = specific heat capacity, T = temperature, Q = heat, t = time From this formula, you would derive that temperature keeps on increasing as long as dQ/dt > 0. But if you, for example, look at the idealized...

Hello everyone, I was hoping to get some insight on a model I am trying to create. Quick background in case it is important, I am now working at a new internship I landed for the summer doing some modeling and what not on areas of physics I have never worked on before. It has also been a few...

I'm reading a thermo book and I'm on the chapter dealing with the first law of thermodynamics. The book is discussing functions of state and how the internal energy is a function of state because it has a well defined value at every equilibrium state of the system. It says that the work and...

Homework Statement The Higher Heating Value (HHV) of gaseous propane is given as 2220.0 kJ/mol. What is the value of the Lower Heating Value (LHV) of gaseous propane? Data for water (all in kJ/mol): H(g, 25 deg. C) = 45.85 ; H(g, 100 deg. C) = 48.17 ; H(l, 25 deg. C) = 1.886 ; H(l, 100 deg. C)...

Homework Statement A satellite to reflect radar is a 3.5-m-diameter, 2.0-mm-thick spherical copper shell. While orbiting the earth, the satellite absorbs sunlight and is warmed to 50 °C. When it passes into the Earth's shadow, the satellite radiates energy to deep space. You can assume a...

Hi everyone I'm having trouble with solving an exercise in statistical physics. I need to argue why the average number of particles with a velocity between ##v## and ##v+dv## that hit a surface area ##A## on the container wall in a time interval ##\Delta t## is $$N_{collision}=v_{x}A\Delta t...

Hi guys! I'm a high school student and I love Physics. I hope this site will help me learn and understand a lot of (new) things! :)

Hey all, I'm currently studying for my thermo final and it's really kicking my butt. My average has been a C and if I do EXTREMELY well on my final I'll be REALLY pushing for a B. I'm not sure how thermo is taught in other universities, but I'm learning it through statistical mechanics with...

Homework Statement Homework Equations PV = nRT \\ W = - \int_{V_i}^{V_f} P dV \Delta E_{int} = Q + W The Attempt at a Solution a)[/B] Since this is a cyclic process, the change in internal energy of the system is 0. \Delta E_{int} = 0 The process causes some ice to melt, meaning heat...

One big coincidence of thermodynamics is that automobiles are usually powered by an Otto cycle This cycle consists of an adiabatic compression (the cylinder compresses), isochoric compression (the fuel ignites, increasing the temperature in too short a time for the piston to move), adiabatic...

Homework Statement 5 moles of liquid argon undergoes vaporization at its normal boiling point (87.5 K) and the resulting argon gas is subsequently heated to 150 K under constant volume conditions. Calculate the change of entropy for this process. The standard enthalpy change of vaporization, ∆...

Calculate the change in entropy for the system, the surroundings and the Universe if 2 moles of ethane are completely combusted at 298 K. Standard entropies of C2H5(g), O2(g), H2O(l) and CO2(g) are 229.6, 205.1, 69.9, 213.7 J mol-1 K-1 , respectively. Standard enthalpy changes of formation of...

Homework Statement The pV-diagram in Fig. P20.51 (See attached file) shows the cycle for a refrigerator operating on 0.850 mol of H2. Assume that the gas can be treated as ideal. Process ab is isothermal. Find the coefficient of performance of this refrigerator. Homework Equations K = QC/|QH -...

I'm trying to build a fanless computer case for a small electronic device. I'm trying to figure out what type of heat-sink material I should use. I have a solid copper rod about 3cm in length with a radius of .05cm. I've determined and calculated the density, specific heat, thermal...

here is the question (part I): For part I, I need some assistance, I cannot figure out how to do the question. I know eventually what to do, it's just working out the equilibrium constants I'm having trouble with. So to start, I want to work out the K values at 600K and 800K, I do this by...

Hi, I am designing a system to cool aluminium through contact cooling. I have a steel die with 9x 20mm diameter cooling chambers. Water is pumped through the chambers which cools the steel die and hopefully the aluminium sitting on top of it. I am looking to find the temperature of the...

Homework Statement : [/B]Find the change in internal energy of 2kg water as it is heated from 0°C to 4°C. The specific heat capacity of water is 4200J/Kg and its densities at 0°C and 4°C are 999.9 kg/m3 and 1000kg/m3 respectively. Atm pressure=105PaHomework Equations :ΔU= Q-W W=PΔV M/V=D[/B]The...

Hello. I read the textbook of the thermodynamic and it said the definition of the reversible process as "thermodynamic process which is slow enough so the system state is always infinitesimally close to the thermodynamic equilibrium (quasi-static) during the process. Such a process can always...

Hi there, I have a problem that I cannot find a solution too. In this problem I have a fuel (approximately natural gas) supply which is combusted when mixed with air inside a burner. The flame that is then generated is used to heat up a sealed cylindrical vessel (the flame is on the outside of...

Homework Statement Integrate w=–∫vDP from 2 to 1 and get k(P2V2-P1V1/1-k) The equation is used for steady flow, reversible and Ideal gas Homework EquationsThe Attempt at a Solution I'm not sure how to get the result

1. The problem statement, all variables, and given/known data Q1 Resistance at 0 degrees Celsius = 3840 ohms Resistance at 100 degrees Celsius = 190 ohms Resistance at ? degrees Celsius = 2300 ohms a. Calculate the temperature of the water according to calibrated thermistor assuming the...

Homework Statement Assume 1.500 mol of a monatomic ideal gas is compressed from 3.00 L to 1.00 L. a. If the initial and final temperature is 10.0 °C, what are the initial and final pressures (in atm)? b. How much work input (in kJ) is required if a reversible isothermal path at 10.0 °C is...

Homework Statement A.[/B] Someone is walking outside when the temperature of the air is -10°C. The metabolic rate of walking is 140 Cal/m2hr, and the usual muscle efficiency (20%) applies. They are completely covered by clothing with a coefficient of thermal conductivity of 0.36 Cal-cm/m2hr...

Homework Statement A closed, rigid tank contains 2 kg of water, initially a two phase liquid–vapor mixture at T1 = 70°C. Heat transfer occurs until the tank contains only saturated vapor at T2 = 120C. Determine the heat transfer for the process, in kJ. answer choices: 3701kJ 119.4kJ 4835kJ...

Hello everyone! I am currently having some real issues estimating the power requirements for a concept vehicle's Air-Conditioning System, and I mean I've been going over this on and off for the better part of a fortnight. At this stage I feel like I have fried my brain and have no idea if I am...

water is flowing in the closed looped pipe equipped with preheater. there are pressure and temperature gauges before the preheater and after the preheater. which pressure gauge should i use to know whether the outlet preheater temperature has reached the saturation temperature?

I bought the drinking bird toy, and I want to get a better understanding of it, (https://en.wikipedia.org/wiki/Drinking_bird) I understand the basic way it works and that it is a simple heat engine, but I can't seem to find any information that helps me answer the following - I notice all...

Homework Statement A train engine climbs a hill. The engine is 30% efficient. The train has a mass of 12000kg. The hill is 750m in height, with an incline of 20° form the horizontal. Friction exerts a force opposing motion of 8000N throughout the climb. Find w, Qin and Qout for the engine...

Homework Statement The tires on a bicycle require an air pressure of 80 psig. When isothermally pumped up the bicycle tires, the volume of the air (that was originally in the atmosphere) is reduced by a factor of 5.7. Please determine the work that must be done on each lbm of air that is pumped...

According to the first law of thermodynamics, dQ = dU + dW and you can find dU = nCvdT If this is the case then when water at 100°C vaporizes to steam at 100°C shouldn't the change in internal energy be zero because it is dependent on temperature change?

Homework Statement I'm given that the energy of a particle in a rectangular box is the following: E =\frac{\hbar \pi^2}{2m}(\frac{n_x^2}{L_x^2}+\frac{n_y^2}{L_y^2}+\frac{n_z^2}{L_z^2}) I'm to show that if the length of the box is increased adiabatically and quasistatically from L_x to 8L_x...

Homework Statement You would like to put a solar hot water system on your roof, but you're not sure it's feasible. A reference book on solar energy shows that the ground-level solar intensity in your city is 750 W/m^2 for at least 5 hours a day throughout most of the year. Assuming that a...

What is wrong with this logic, if any? It does not seem like this should be true but maybe I'm mistaken. Assuming the process consists of two isobaric processes and two isothermal processes the work from B to C in terms of p1, p2, V1, and V2 is given by the following. 1) WBC=p2(VC-VB) 2)...

Homework Statement "A well-insulated bucket of negligible heat capacity contains 120 g of ice at 0°C. If 20 g of steam at 100°C is injected into the bucket, what is the final equilibrium temperature of the system?" Homework Equations $$Q_{fus} = m_{water}L_{fus}$$ $$Q_{vap} =...

Homework Statement In a container of negligible mass, equal amounts (in weight) of ice at 0°C and steam at 100°C are mixed at atmospheric pressure. Assuming no heat exchange with the surroundings, what is the temperature when the system reaches equilibrium? What are the fractions of weights of...

What is the physics behind heat transfer between two panes of glass? Commonly windows now are filled with argon (some cost) or krypton (pricey) At a given temperature all gas molecules have the same energy per mode, so heavy ideal gas molecules move more slowly than light ones, so heat...

Homework Statement Consider an Ideal gas engine with the following cycle: i. Isobaric expansion (T1 -> Th) ii. adiabatic expansion (Th -> T2) iii. Isobaric compression (T2 -> T_L) iv. adiabatic compression (T_L -> T1) a. Find its efficiency b. When operated in two temperature, show that Carnot...

I've been given the following relations where as I understand it subindex 2 equals subindex e and subindex 1 equals subindex i: ***EDIT*** More accurately subindex 1; initial state of a control mass subindex 2: end state of a control mass (end state is simply state 2 in the problem at hand)...

Homework Statement A 1.250 g sample of ##C_8H_18## is burnt with excess oxygen in a bomb calorimeter. Change in temperature is from 294.05 K to 300.78 K. If heat capacity of the calorimeter is 8.93 kJ/K. Find the heat transferred to the calorimeter. Also calculate the enthalpy of combustion of...

This table is given in my book, $$\begin{array}[c!c!c!c!] \text{ }&\text{ Transitional }&\text{ Rotational }& \text{ Vibrational} \\ \hline \text{Linear molecules} & 3&2& 3N -5\\ \hline \text{Non-Linear molecules} & 3&3& 3N -6\\ \hline \end{array}$$ It is also given...

I have read Average translation kinetic energy is 1/2RT per degree of freedom and Average translation kinetic energy for an ideal gases is 3/2RT.How? Does it imply f=3 for all ideal gases?

Homework Statement Suppose you are given the following relation among the entropy S, volume V , internal energy U, and number of particles N of a thermodynamic system, where A is a constant.: $$ S = A(NVU)^{\frac 1 3} $$ Find the chemical potential μ(T,P) Homework Equations $$ \frac μ T =...

When calculating heat transfer, how would one know when to use Q=T*m*(delta s) versus Q=m*(delta h). I'm confused when we should calculate using entropy versus enthalpy. Anything helps. Thank you!

Homework Statement As shown in figure. Homework Equations dq=msdt[/B]The Attempt at a Solution I am unable to understand the question,what is the significance of the moving piston if the ends of the conducting rod is maintained at constant temperature.It is enough if someone could explain...

Homework Statement Im working on the following problem and could need some help in answering them: Work is being produced from a cycle. In order to produce this work, energy is being taking from a high temperature sources at a ratio of 1000 kJ/kg and the extra energy is being deliver to a...